There are many types of so-called 3-D display devices on the market which are not truly 3-D but in fact produce a 2-D image on a screen which is made to appear as a 3-D image. Attempts have been made to create real 3-D moving displays. One such device described in U.S. Pat. No. 4,023,158 (Corcoran) uses a laser beam to levitate glass spheres to produce a 3-D display. Another device described in U.S. Pat. No. 3,789,397 (Evans) proposes to create a 3-D display by intersecting two or more laser beams to create a spot of illumination. Evans claims that his two lasers will intersect to produce a "hot spot" or "visible spot". Evans does not describe the nature of this "hot spot" or "visible spot" or any of the details of the laser beams which he would use to produce it. Typically, intersecting laser beams will not produce a visible spot. Evans indicates that the laser beams intersect in an atmosphere which may be air or some other selected atmosphere but he does not otherwise disclose what the atmosphere should be.